Php 左键连接两个表、多个列

我需要左键连接两个表：

Cardealers

和

Applications

我想看看哪些持卡人收到了哪些申请

每个应用程序都转发给三个Cardealer，因此我的表结构有以下三列：

receiver_1

，

receiver_2

，

receiver_3

其中，接收器列中的ID与

cardealer\u ID

相同

我的代码仅适用于一列和一列：

$res1 = $wpdb->get_results( " SELECT leads.*, cardealers.*
    FROM leads
    LEFT JOIN cardealers ON leads.receiver_1 = cardealers.cardealer_id
    WHERE leads.receiver_1 = cardealers.cardealer_id
    AND cardealers.cardealer_id = '". $cardealer_id ."'" );

$res2 = $wpdb->get_results( " SELECT leads.*, cardealers.*
    FROM leads
    LEFT JOIN cardealers ON leads.receiver_2 = cardealers.cardealer_id
    WHERE leads.receiver_2 = cardealers.cardealer_id
    AND cardealers.cardealer_id = '". $cardealer_id ."'" ); 

$res3 = $wpdb->get_results( " SELECT leads.*, cardealers.*
    FROM leads
    LEFT JOIN cardealers ON leads.receiver_3 = cardealers.cardealer_id
    WHERE leads.receiver_3 = cardealers.cardealer_id
    AND cardealers.cardealer_id = '". $cardealer_id ."'" );

正如你所看到的，我做了3个独立的陈述，它们都是有效的。但我想把这些结合成一句话

---

我该怎么做

只需继续添加表并为它们添加别名即可

SELECT 
   leads.*, cardealers1.*, cardealers2.*, cardealers3* 
FROM leads 
LEFT JOIN cardealers as cardealers1
   ON leads.receiver_1 = cardealers1.cardealer_id 
LEFT JOIN cardealers as cardealers2
   ON leads.receiver_2 = cardealers2.cardealer_id
LEFT JOIN cardealers as cardealers3
   ON leads.receiver_3 = cardealers3.cardealer_id
WHERE 
   leads.receiver_1 = cardealers1.cardealer_id 
   AND leads.receiver_2 = cardealers2.cardealer_id 
   AND leads.receiver_3 = cardealers3.cardealer_id 
   AND cardealers.cardealer_id = '". $cardealer_id ."'

---

编辑：最好为每个Cardealer的列指定一个别名

请参见规范化。每当你列举了列（比如“2”以上），你的设计可能出了问题。嗨@Tah Tatsumoto谢谢你的快速回复。它现在不起作用。我根据POST请求进行查询。其中$cardealer_id对应于该id。在代码的最后一行中，它表示：cardealers.cardealer_id='“$cardealer_id.”1。在这前面不是有一个和失踪的人吗？2.我需要复制这个吗？比如cardealers1.cardealer\u id=“$cardealer\u id.”，cardealers2.cardealer\u id=“$cardealer\u id.”等等？